I run dependency walker on a new machine and profiled the application which produced this error yet my app includes qwindows.dll in the platforms directory.

@LoadLibraryW("C:\program files\theapp\platforms\qwindows.dll") returned NULL. Error: The specified procedure could not be found (127).
Failed to load platform plugin "windows". Available platforms are:
windows@

On the clear machine (without Qt instalation) you should put your app in one folder with all *.dll's needed (e.g. QtGui.dll, QtWidgets.dll, etc). In this same folder you should put folder "platforms" with qwindows.dll, folder printsupport with its dll's and so on). I dont know, what is your app and which libraries of Qt it needs exactly.

Sorry, i don't understood your firs post. The line "LoadLibraryW(..." it is message from Dependency Walker, isn't it? I have no idea, why it dont work. Maby it is problem with location your folder with app on C:\ (problem UAC in windows?) I utilize method desribed below and i havn't problems yet, but my default localisation of apps is logical disk d:\programms. Let search forums for similar threads, perhaps you'll find the ansver.
Best regards.

In the past I have had the same problem (using mingw).
If you want you can download this packagehttp://www.denisgottardello.it/BackupTo/BackupTo.php
and look at the dlls and plugins. Remember that you have to specify the plusing location using qt.conf special file.